In 1998, a murder occurred on a rainy night in the old factory area of Sioux City.
Fourteen-year-old Chen Mo killed Lin Xueying's father and disappeared from her life.
In the next eighteen years, several unsolved cases occurred in Sioux City. The victims have one thing in common, they all have hindered Lin Xueying from moving forward. And at every crime scene, a mysterious symbol is left: a cross inside a circle.
Zhe, the criminal police officer responsible for investigating these cases, gradually saw the truth clearly: Chen Mo never left. He was like a shadow, eliminating all threats for her. And she lived a glorious life with two people in mind.
For eighteen years, they never met or contacted each other. But every symbol he carved on the crime scene was like a wordless letter to her.
The half circle she drew in the air late at night in an empty art museum was a reply that would never be sent.
It's an indefinable symbiosis. One person makes another person's life his own continuation.
Until the end, when she had to choose between him and herself, she pointed the way for him with her own hands.
He knew it was a trap, but he went anyway.
At the scene of his death, she turned away and never looked back.
Intention: Some love cannot see the light, but burns for the other person in the dark for a lifetime.